1. Field of the Invention
The present invention relates to agricultural vehicles, and, more particularly, to combine harvesters.
2. Description of the Related Art
Combines are used to harvest agricultural crops such as corn, soybeans, wheat and other grain crops. As the combine is driven through crop fields, the combine cuts the crop, separates the desired crop from the undesired waste, stores the crop, and discards the waste.
In a typical combine, a header is mounted to the front of the combine to gather the crop and feed the crop into the combine for processing. As the combine is driven through the field, the crop material is collected by the header and deposited into a feeder housing. The crop material is then transported upwardly and into the combine by a feed elevator located within the feeder housing. The crop material then passes through a threshing and separating mechanism. In a rotary combine, the threshing and separating mechanism includes a rotor, a threshing concave, a rotor cage, and a separating grate. As crop material passes between the rotor, the threshing concave and the separating grate, the crop material is impacted and/or rubbed, thereby causing the grain to separate from the stalk material. The stalk material that is separated from the grain is commonly referred to as material other than grain (MOG). Other types of combines are also known that perform similar functions using different mechanisms.
After passing through the threshing and separating assembly, the grain and MOG are deposited onto a grain cleaning system. The grain cleaning system of a typical combine includes a plurality of adjustable cleaning sieves, often referred to as a chaffer sieve and a shoe sieve, and may also include a pan between the threshing and separating assembly and the cleaning sieves. The sieves are typically reciprocated back and forth in opposite directions along an arcuate path. This motion has the tendency to separate the grain from the MOG. To further separate the grain from the MOG, a cleaning fan or blower is positioned so as to blow air up through the cleaning sieves. This flow of air tends to blow the MOG, which is typically lighter than grain, rearwardly and out the back of the combine. Grain, which is heavier than MOG, is allowed to drop through the openings in the sieve.
The clean grain that falls through the cleaning sieves is deposited on a collection panel positioned beneath the cleaning sieves. The collection panel is angled so as to permit the grain to flow, under the influence of gravity, into an auger trough positioned along the lowermost edge of the collection panel. The auger trough is typically positioned near the forward end of the cleaning sieves and extends along the width of the sieves. The grain collected in the auger trough is then moved by an auger towards the side of the combine where it is raised by a grain elevator and deposited into a storage tank or grain tank. Other systems also exist that can utilize, for example, a loop conveyor system which eliminates the need for a conventional cross auger.
Since the combine is simultaneously collecting and cleaning crop material, the cleaning system can be subjected to changing conditions as the combine navigates a field, affecting the performance of the cleaning system. One particular condition that affects cleaning system performance is when the combine is collecting crop material from a hill or other terrain that is not flat. In such instances, one lateral side of the combine might be angled downwardly with respect to the other lateral side of the combine. This can cause the cleaning system to be similarly angled, with one lateral side of the pan and cleaning sieves being angled downwardly with respect to the other lateral side.
When the pan and/or cleaning sieves are angled in such a way, crop material that is placed on the pan and/or sieves is forced by gravity toward the lateral side that is angled downwardly. This causes the crop material to accumulate on the downward side, which can overwhelm the cleaning sieves' cleaning capacity near the accumulated crop material while leaving other portions of the cleaning sieves with little to no crop material being cleaned and is an inefficient use of the surface area of the cleaning sieves. As the cleaning system optimally functions when crop material is evenly distributed across the effective cleaning surface of the cleaning sieves, evenly distributing crop material on the sieves remains a challenge in designing combine cleaning systems.
One approach to dealing with crop collection and cleaning on an incline is described in U.S. Pat. No. 4,897,071 to Desnijder et al. Desnijder et al. utilize an incline detecting sensor to determine when the machine is on an incline and responsively adjust the lateral tilting of the upper sieve. The configuration taught by Desnijder et al. is commonly referred to as a “self-leveling sieve” system, as the sieve will responsively pivot so the sieve remains a horizontal surface and the crop material does not drift further under the influence of gravity. One limitation to the configuration taught by Desnijder et al. is that the system can only respond to inclination to prevent further crop material drift; the configuration does not correct crop material drift that has already occurred. Further, there can be a lag period between detecting the inclination and responsively adjusting the tilt of the sieve, as well as detecting the machine is back on flat ground and responsively returning the sieve to its original orientation.
What is needed in the art is an agricultural vehicle that allows for more even distribution of crop material to the cleaning sieves when the vehicle is on uneven terrain than known vehicles.